Growth factors are important mediators of intercellular communication. These potent molecules are generally released by one cell type and act to influence proliferation of other cell types (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292). Interest in growth factors has been heightened by evidence of their potential involvement in neoplasia (Sporn, M. B. and Todaro, G. J., 1980, N. Eng. J. Med. 303, 878-880). The v-sis transforming gene of simian sarcoma virus encodes a protein that is homologous to the B chain of platelet-derived growth factor (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292, Doolittle, R. F., et al., 1983, Science 221, 275-277). Moreover, a number of oncogenes are homologues of genes encoding growth factor receptors (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292). Thus, increased understanding of growth factors and their receptor-mediated signal transduction pathways is likely to provide insights into mechanisms of both normal and malignant cell growth.
One known family of growth factors affecting connective tissue cells includes acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFBF), and the related products of the hst, FGF-5 and int-2 oncogenes.
Further, it is known that some growth factors, including the following, have heparin-binding properties: aFGF (Maciag, T., et al., 1984, Science 225, 932-935, Conn, G. and Hatcher, V. B. (1984) Biochem. Biophys. Res. Comm, 124, 262-268); bFGF (Gospodarowicz, D., et al., 1984, Proc. Natl. Acad. Sci. USA 81, 6963-6967, Maciag, T., et al., 1984, Science 225, 932-935); granulocyte/macrophage colony stimulating factor (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292); and interleukin 3 (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292). Each of these polypeptide factors is produced by stromal cells (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292, Doolittle, R. F., et al., 1983, Science 221, 275-277, Roberts, R., et al., 1988, Nature 332, 376-378). Such factors appear to be deposited in the extracellular matrix, or on proteoglycans coating the stromal cell surface (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292, Roberts, R., et al., 1988, Nature 332, 376-378). It has been postulated that their storage, release and contact with specific target cells are regulated by this interaction (Roberts, R., et al., 1988, Nature 332, 376-378, Vlodavsky, I., et al., 1987, Proc. Natl. Acad. Sci. USA 84, 2292-2296).
It is widely recognized, however, that the vast majority of human malignancies are derived from epithelial tissues (Wright, N. and Allison, M., 1984, The Biology of Epithelial Cell Populations [Oxford University Press, New York] Vol. 1, pp. 3-5). Effectors of epithelial cell proliferation derived from mesenchymal cells have been described (James, R. and Bradshaw, R. A., 1984, Ann. Rev. Biochem. 53, 259-292, Doolittle, R. F., et al., 1983, Science 221, 275-277, Waterfield, M. D., et al., 1983, Nature 304, 35-39), however, their molecular identities and structures have not been elucidated.
In light of this dearth of knowledge about such mesenchymal growth factors affecting epithelial cells, it is apparent that there has been a need for methods and compositions and bioassays which would provide an improved knowledge and analysis of mechanisms of regulation of epithelial cell proliferation, and, ultimately, a need for novel diagnostics and therapies based on the factors involved therein.
This invention contemplates the application of methods of protein isolation and recombinant DNA technologies to fulfill such needs and to develop means for producing protein factors of mesenchymal origin, which appear to be related to epithelial cell proliferation processes and which could not be produced otherwise. This invention also contemplates the application of the molecular mechanisms of these factors related to epithelial cell growth processes.